Non-volatile counters are used in various electronic applications. One important application for non-volatile counters is in the field of electronic commerce where it is important to order financial transactions in a definite sequence. In such applications it is important that the counting function be robust enough to withstand hardware and/or software failures, including unexpected power loss. It is also important for the counting function to be secure against unauthorized access and tampering.
One technique for providing a counting function that can withstand power loss is to use a battery or similar power supply in conjunction with a binary counter circuit. Unfortunately, battery-backed counters tend to occupy a relatively large amount of circuit or device space and impose high battery costs. Also, batteries are prone to failure and discharge and so must be monitored and periodically replaced to prevent loss of the count data. Further, many binary counters do not allow for easy recovery of count data in the event of count interruption due to power loss.